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        // 1.绝对值方法
        console.log(Math.abs(1));
        console.log(Math.abs(-1));
        console.log(Math.abs('-1')); //隐式转换 会把字符串型 转换成数字型
        console.log(Math.abs('pnk')); //NaN

        // 2.三个取整方法
        // (1) Math.floor() 向下取整 往最小了取值
        console.log(Math.floor(1.1)); //1
        console.log(Math.floor(1.9)); //1
        // (2) Math.ceil() 向上取整 往最大了取值
        console.log(Math.ceil(1.1)); //2
        console.log(Math.ceil(1.9)); //2
        // (3) Math.round() 四舍五入 其他数字都是四舍五入，但是.5特殊 它往大了取
        console.log(Math.round(1.1)); //1
        console.log(Math.round(1.5)); //2
        console.log(Math.round(-1.1)); //-1
        console.log(Math.round(-1.5)); //-1
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